Visual Debugger & Time-Travel

Overview

Building complex integration workflows requires granular visibility into data transformations at each step. nLink introduces two powerful features to address this:

• Visual Debug Stepper: An interactive mode that allows you to execute your workflow node-by-node, pause execution to inspect the state, and manually override data on the fly.
• Time-Travel (Timeline Slider): A post-execution visual tool that lets you scrub back and forth through the history of a workflow execution, providing a chronological view of how loops, branches, and errors unfolded.

Visual Debug Stepper

The Visual Debug Stepper operates as an isolated sandbox environment. When active, it strictly prevents accidental topology mutations (such as adding nodes or deleting edges), allowing you to focus entirely on the data flow.

1. Starting a Debug Session

Click the Debug button in the workflow header to enter Debug Mode. The interface will switch context, displaying the Debug Mode banner and hiding all workflow mutation controls.

2. Step-by-Step Execution

When you trigger the workflow (e.g., via a Webhook or Manual Trigger), the execution pauses at the first node. You can then:

• Continue: Execute the current node and pause at the next.
• Stop Debug: Immediately halt the execution and clean up the visual state.

3. Debug Data Override (Data Mocking)

Before a node executes, you may want to test its behavior with specific data without modifying upstream nodes.

Click the Config (Gear) icon on the pending node to open its settings. You will see a Debug Data Override section. The system automatically pre-fills this field with the expected JSON structure based on the output of upstream nodes. You can edit this JSON to mock the incoming data for the current node.

{
  "main": [
    {
      "json": {
        "mocked_field": "custom_test_value"
      }
    }
  ]
}

Time-Travel (Execution Timeline)

After a workflow finishes execution, or when viewing a past execution from the Execution History logs, nLink presents a Timeline Slider at the bottom of the screen.

This feature leverages an optimized $O(N+M)$ Hash Map algorithm to map the chronological executionManifest onto the $M$ nodes of your visual graph.

• Chronological Scrubbing: Drag the slider left or right to move forward or backward in time.
• Loop Visibility: If a workflow contains loops (executing the same node multiple times), dragging the slider will accurately reflect the latest state of that node up to that specific point in time.
• Visual Cues: Nodes will highlight in green (success) or red (error), and edges will display dashed animations indicating the exact path the data traversed.

Safety Mechanisms

To ensure a robust debugging experience, the following constraints are enforced when Debug Mode is active:

• Graph Lock-down: Adding nodes, deleting nodes or edges, and modifying connections are strictly disabled.
• Keyboard Shortcuts Disabled: Delete/Backspace and Ctrl+V (Paste) are intercepted to prevent accidental canvas mutations.
• State Isolation: Stopping a debug session immediately cleans up all temporary visual states (e.g., running gradients, error borders, edge animations) without affecting the actual workflow definition.